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Subject: Re: [f2fs-dev] [PATCH 1/2] f2fs: support aligned pinned file
To:     Jaegeuk Kim <jaegeuk@kernel.org>
CC:     <linux-kernel@vger.kernel.org>,
        <linux-f2fs-devel@lists.sourceforge.net>
References: <20191022171602.93637-1-jaegeuk@kernel.org>
 <c916c749-0abe-a7b7-e748-f0c4d5599e4a@huawei.com>
 <20191025181820.GA24183@jaegeuk-macbookpro.roam.corp.google.com>
From:   Chao Yu <yuchao0@huawei.com>
Message-ID: <8cfef676-e81f-6069-3b0b-7005fbf8e0bb@huawei.com>
Date:   Sat, 26 Oct 2019 09:31:16 +0800
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On 2019/10/26 2:18, Jaegeuk Kim wrote:
> On 10/24, Chao Yu wrote:
>> Hi Jaegeuk,
>>
>> On 2019/10/23 1:16, Jaegeuk Kim wrote:
>>> This patch supports 2MB-aligned pinned file, which can guarantee no GC at all
>>> by allocating fully valid 2MB segment.
>>>
>>> Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
>>> ---
>>>  fs/f2fs/f2fs.h     |  4 +++-
>>>  fs/f2fs/file.c     | 39 ++++++++++++++++++++++++++++++++++-----
>>>  fs/f2fs/recovery.c |  2 +-
>>>  fs/f2fs/segment.c  | 21 ++++++++++++++++++++-
>>>  fs/f2fs/segment.h  |  2 ++
>>>  fs/f2fs/super.c    |  1 +
>>>  fs/f2fs/sysfs.c    |  2 ++
>>>  7 files changed, 63 insertions(+), 8 deletions(-)
>>>
>>> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
>>> index ca342f4c7db1..c681f51e351b 100644
>>> --- a/fs/f2fs/f2fs.h
>>> +++ b/fs/f2fs/f2fs.h
>>> @@ -890,6 +890,7 @@ enum {
>>>  	CURSEG_WARM_NODE,	/* direct node blocks of normal files */
>>>  	CURSEG_COLD_NODE,	/* indirect node blocks */
>>>  	NO_CHECK_TYPE,
>>> +	CURSEG_COLD_DATA_PINNED,/* cold data for pinned file */
>>>  };
>>>  
>>>  struct flush_cmd {
>>> @@ -1301,6 +1302,7 @@ struct f2fs_sb_info {
>>>  
>>>  	/* threshold for gc trials on pinned files */
>>>  	u64 gc_pin_file_threshold;
>>> +	struct rw_semaphore pin_sem;
>>>  
>>>  	/* maximum # of trials to find a victim segment for SSR and GC */
>>>  	unsigned int max_victim_search;
>>> @@ -3116,7 +3118,7 @@ void f2fs_release_discard_addrs(struct f2fs_sb_info *sbi);
>>>  int f2fs_npages_for_summary_flush(struct f2fs_sb_info *sbi, bool for_ra);
>>>  void allocate_segment_for_resize(struct f2fs_sb_info *sbi, int type,
>>>  					unsigned int start, unsigned int end);
>>> -void f2fs_allocate_new_segments(struct f2fs_sb_info *sbi);
>>> +void f2fs_allocate_new_segments(struct f2fs_sb_info *sbi, int type);
>>>  int f2fs_trim_fs(struct f2fs_sb_info *sbi, struct fstrim_range *range);
>>>  bool f2fs_exist_trim_candidates(struct f2fs_sb_info *sbi,
>>>  					struct cp_control *cpc);
>>> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
>>> index 29bc0a542759..f6c038e8a6a7 100644
>>> --- a/fs/f2fs/file.c
>>> +++ b/fs/f2fs/file.c
>>> @@ -1545,12 +1545,41 @@ static int expand_inode_data(struct inode *inode, loff_t offset,
>>>  	if (off_end)
>>>  		map.m_len++;
>>>  
>>> -	if (f2fs_is_pinned_file(inode))
>>> -		map.m_seg_type = CURSEG_COLD_DATA;
>>> +	if (!map.m_len)
>>> +		return 0;
>>> +
>>> +	if (f2fs_is_pinned_file(inode)) {
>>> +		block_t len = (map.m_len >> sbi->log_blocks_per_seg) <<
>>> +					sbi->log_blocks_per_seg;
>>> +		block_t done = 0;
>>> +
>>> +		if (map.m_len % sbi->blocks_per_seg)
>>> +			len += sbi->blocks_per_seg;
>>>  
>>> -	err = f2fs_map_blocks(inode, &map, 1, (f2fs_is_pinned_file(inode) ?
>>> -						F2FS_GET_BLOCK_PRE_DIO :
>>> -						F2FS_GET_BLOCK_PRE_AIO));
>>> +		map.m_len = sbi->blocks_per_seg;
>>> +next_alloc:
>>> +		mutex_lock(&sbi->gc_mutex);
>>> +		err = f2fs_gc(sbi, true, false, NULL_SEGNO);
>>> +		if (err && err != -ENODATA && err != -EAGAIN)
>>> +			goto out_err;
>>
>> To grab enough free space?
>>
>> Shouldn't we call
>>
>> 	if (has_not_enough_free_secs(sbi, 0, 0)) {
>> 		mutex_lock(&sbi->gc_mutex);
>> 		f2fs_gc(sbi, false, false, NULL_SEGNO);
>> 	}
> 
> The above calls gc all the time. Do we need this?

Hmmm... my concern is why we need to run foreground GC even if there is enough
free space..

> 
>>
>>> +
>>> +		down_write(&sbi->pin_sem);
>>> +		map.m_seg_type = CURSEG_COLD_DATA_PINNED;
>>> +		f2fs_allocate_new_segments(sbi, CURSEG_COLD_DATA);
>>> +		err = f2fs_map_blocks(inode, &map, 1, F2FS_GET_BLOCK_PRE_DIO);
>>> +		up_write(&sbi->pin_sem);
>>> +
>>> +		done += map.m_len;
>>> +		len -= map.m_len;
>>> +		map.m_lblk += map.m_len;
>>> +		if (!err && len)
>>> +			goto next_alloc;
>>> +
>>> +		map.m_len = done;
>>> +	} else {
>>> +		err = f2fs_map_blocks(inode, &map, 1, F2FS_GET_BLOCK_PRE_AIO);
>>> +	}
>>> +out_err:
>>>  	if (err) {
>>>  		pgoff_t last_off;
>>>  
>>> diff --git a/fs/f2fs/recovery.c b/fs/f2fs/recovery.c
>>> index 783773e4560d..76477f71d4ee 100644
>>> --- a/fs/f2fs/recovery.c
>>> +++ b/fs/f2fs/recovery.c
>>> @@ -711,7 +711,7 @@ static int recover_data(struct f2fs_sb_info *sbi, struct list_head *inode_list,
>>>  		f2fs_put_page(page, 1);
>>>  	}
>>>  	if (!err)
>>> -		f2fs_allocate_new_segments(sbi);
>>> +		f2fs_allocate_new_segments(sbi, NO_CHECK_TYPE);
>>>  	return err;
>>>  }
>>>  
>>> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
>>> index 25c750cd0272..253d72c2663c 100644
>>> --- a/fs/f2fs/segment.c
>>> +++ b/fs/f2fs/segment.c
>>> @@ -2690,7 +2690,7 @@ void allocate_segment_for_resize(struct f2fs_sb_info *sbi, int type,
>>>  	up_read(&SM_I(sbi)->curseg_lock);
>>>  }
>>>  
>>> -void f2fs_allocate_new_segments(struct f2fs_sb_info *sbi)
>>> +void f2fs_allocate_new_segments(struct f2fs_sb_info *sbi, int type)
>>>  {
>>>  	struct curseg_info *curseg;
>>>  	unsigned int old_segno;
>>> @@ -2699,6 +2699,9 @@ void f2fs_allocate_new_segments(struct f2fs_sb_info *sbi)
>>>  	down_write(&SIT_I(sbi)->sentry_lock);
>>>  
>>>  	for (i = CURSEG_HOT_DATA; i <= CURSEG_COLD_DATA; i++) {
>>> +		if (type != NO_CHECK_TYPE && i != type)
>>> +			continue;
>>> +
>>>  		curseg = CURSEG_I(sbi, i);
>>>  		old_segno = curseg->segno;
>>>  		SIT_I(sbi)->s_ops->allocate_segment(sbi, i, true);
>>> @@ -3068,6 +3071,19 @@ void f2fs_allocate_data_block(struct f2fs_sb_info *sbi, struct page *page,
>>>  {
>>>  	struct sit_info *sit_i = SIT_I(sbi);
>>>  	struct curseg_info *curseg = CURSEG_I(sbi, type);
>>> +	bool put_pin_sem = false;
>>> +
>>> +	if (type == CURSEG_COLD_DATA) {
>>> +		/* GC during CURSEG_COLD_DATA_PINNED allocation */
>>> +		if (down_read_trylock(&sbi->pin_sem)) {
>>> +			put_pin_sem = true;
>>> +		} else {
>>> +			type = CURSEG_WARM_DATA;
>>> +			curseg = CURSEG_I(sbi, type);
>>
>> It will mix pending cold data into warm area... rather than recovering curseg to
>> write pointer of last cold segment?
>>
>> I know maybe that fallocate aligned address could be corner case, but I guess
>> there should be some better solutions can handle race case more effectively.
>>
>> One solution could be: allocating a virtual log header to select free segment as
>> 2m-aligned space target.
> 
> I thought about that, but concluded to avoid too much changes.

We have an unupstreamed feature which is based on virtual log header, I can
introduce that basic virtual log fwk, which can be used for aligned allocation
and later new features, would you like to check that?

Thanks,

> 
>>
>> Thanks,
>>
>>> +		}
>>> +	} else if (type == CURSEG_COLD_DATA_PINNED) {
>>> +		type = CURSEG_COLD_DATA;
>>> +	}
>>>  
>>>  	down_read(&SM_I(sbi)->curseg_lock);
>>>  
>>> @@ -3133,6 +3149,9 @@ void f2fs_allocate_data_block(struct f2fs_sb_info *sbi, struct page *page,
>>>  	mutex_unlock(&curseg->curseg_mutex);
>>>  
>>>  	up_read(&SM_I(sbi)->curseg_lock);
>>> +
>>> +	if (put_pin_sem)
>>> +		up_read(&sbi->pin_sem);
>>>  }
>>>  
>>>  static void update_device_state(struct f2fs_io_info *fio)
>>> diff --git a/fs/f2fs/segment.h b/fs/f2fs/segment.h
>>> index 325781a1ae4d..a95467b202ea 100644
>>> --- a/fs/f2fs/segment.h
>>> +++ b/fs/f2fs/segment.h
>>> @@ -313,6 +313,8 @@ struct sit_entry_set {
>>>   */
>>>  static inline struct curseg_info *CURSEG_I(struct f2fs_sb_info *sbi, int type)
>>>  {
>>> +	if (type == CURSEG_COLD_DATA_PINNED)
>>> +		type = CURSEG_COLD_DATA;
>>>  	return (struct curseg_info *)(SM_I(sbi)->curseg_array + type);
>>>  }
>>>  
>>> diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
>>> index f320fd11db48..c02a47ce551b 100644
>>> --- a/fs/f2fs/super.c
>>> +++ b/fs/f2fs/super.c
>>> @@ -2853,6 +2853,7 @@ static void init_sb_info(struct f2fs_sb_info *sbi)
>>>  	spin_lock_init(&sbi->dev_lock);
>>>  
>>>  	init_rwsem(&sbi->sb_lock);
>>> +	init_rwsem(&sbi->pin_sem);
>>>  }
>>>  
>>>  static int init_percpu_info(struct f2fs_sb_info *sbi)
>>> diff --git a/fs/f2fs/sysfs.c b/fs/f2fs/sysfs.c
>>> index b558b64a4c9c..f164959e4224 100644
>>> --- a/fs/f2fs/sysfs.c
>>> +++ b/fs/f2fs/sysfs.c
>>> @@ -154,6 +154,8 @@ static ssize_t features_show(struct f2fs_attr *a,
>>>  	if (f2fs_sb_has_casefold(sbi))
>>>  		len += snprintf(buf + len, PAGE_SIZE - len, "%s%s",
>>>  				len ? ", " : "", "casefold");
>>> +	len += snprintf(buf + len, PAGE_SIZE - len, "%s%s",
>>> +				len ? ", " : "", "pin_file");
>>>  	len += snprintf(buf + len, PAGE_SIZE - len, "\n");
>>>  	return len;
>>>  }
>>>
> .
>